Quinolinemethine dyes

ABSTRACT

Quinolinemethine dyes suitable for use in a thermal transfer process have the formula ##STR1## where R 1  is fluorine, chlorine or bromine, 
     R 2  is hydrogen or C 1  -C 4  -alkyl, 
     R 3  is hydrogen, fluorine, chlorine or bromine, and 
     K is the radical of an aniline derivative.

The present invention relates to novel quinolinemethine dyes of theformula I ##STR2## where R¹ is fluorine, chlorine or bromine,

R² is hydrogen or C₁ -C₄ -alkyl,

R³ is hydrogen, fluorine, chlorine or bromine, and

K is a radical of the formula ##STR3## where R⁴ is hydrogen, methyl,methoxy, C₁ -C₄ -alkyl-sulfonylamino, C₁ -C₄ -mono- or-dialkylamino-sulfonylamino or the radical -NHCOR⁸ or -NHCO₂ R⁸, wherer⁸ is phenyl, benzyl, tolyl or C₁ -C₈ -alkyl which may be interrupted byone or two oxygen atoms in ether function,

R⁵ is hydrogen, methoxy or ethoxy, and

R⁶ and R⁷ are identical or different and each is independently of theother hydrogen, C₁ -C₈ -alkyl which may be substituted and which may beinterrupted by one or two oxygen atoms in ether function, or C₅ -C₇-cycloalkyl,

and to a process for the thermal transfer thereof.

JP-A-19 396/1986 discloses quinolinemethine dyes in which ring position7 of the quinoline ring is unsubstituted.

Furthermore, JP-A-84 388/1990 and U.S. Pat. No. 4,769,360 describenaphthoquinoneimine dyes which have a chlorine or iodine atom in theortho-position relative to the carbonyl group.

However, it has been found that the prior art dyes still havedeficiencies in their application properties.

It is an object of the present invention to provide novelquinolinemethine dyes which are advantageously suitable for thermaltransfer.

We have found that this object is achieved by the quinolinemethine dyesof the formula I defined at the beginning.

Any alkyl appearing in the abovementioned formula I may bestraight-chain or branched.

Substituted alkyl appearing in the abovementioned formula I may possessas substituents for example cyano, phenyl, tolyl, C₁ -C₆ -alkanoyloxy,C₁ -C₄ -alkoxycarbonyl or C₁ -C₄ -alkoxycarbonyloxy, of which in thelast-mentioned case the alkoxy group may be substituted by phenyl or C₁-C₄ -alkoxy.

Suitable R², R⁶, R⁷ and R⁸ radicals are for example methyl, ethyl,propyl, isopropyl, butyl, isobutyl and sec-butyl.

R⁶, R⁷ and R⁸ may each also be for example pentyl, isopentyl, neopentyl,tert-pentyl, hexyl,-2-methylpentyl, heptyl, octyl, 2-ethylhexyl,2-methoxyethyl, 2- or 3-methoxypropyl, 2-ethoxyethyl, 2- or3-ethoxypropyl, 2-propoxyethyl, 2- or 3-propoxypropyl, 2-butoxyethyl,2-or 3-butoxypropyl, 3,6-dioxaheptyl or 3,6-dioxaoctyl.

R⁶ and R⁷ may each also be for example -cyanoethyl, 2- or 3-cyanopropyl,2-acetyloxyethyl, 2-or 3-acetyloxypropyl, 2-isobutyryloxyethyl, 2-or3-isobutyryloxypropyl, 2-methoxycarbonylethyl, 2- or3-methoxycarbonylpropyl, 2-ethoxycarbonylethyl, 2- or3-ethoxycarbonylpropyl 2-methoxycarbonyloxyethyl, 2- or3-methoxycarbonyloxypropyl, 2-ethoxycarbonyloxyethyl, 2-or3-ethoxycarbonyloxypropyl, 2-propoxycarbonyloxyethyl, 2- or3-propoxylcarbonyloxypropyl, 2-butoxycarbonyl-oxyethyl, 2- or3-butoxycarbonyloxypropyl, 2-(2-phenylethoxycarbonyloxy)ethyl, 2- or3-(2-phenylethoxycarbonyloxy) propyl, 2 - ( 2 -ethoxyethoxycarbonyloxy)ethyl , 2 - or 3-(2-ethoxyetho xycarbonylo xy)propyl, benzyl,2-methylbenzyl, 1- or 2-phenylethyl, cyclopentyl, cyclohexyl ofcycloheptyl.

R⁴ is for example methylsulfonylamino, ethyl-sulfonylamino,propylsulfonylamino, isopropylsulfonyl-amino, butylsulfonylamino, mono-or dimethylamino-sulfonylamino, mono- or diethylaminosulfonylamino,mono-or dipropylaminosulfonylamino, mono- ordiisopropylamino-sulfonylamino, mono- or dibutylaminosulfonylamino or(N-methyl-N-ethylaminosulfonyl)amino.

Preference is given to quinolinemethine dyes of the formula I where

R¹ is chlorine,

R² is hydrogen or methyl,

R³ is hydrogen, and

K is a radical of the formula IIa, IIc, IIe, IIf or IIg.

Emphasis must be given to quinolinemethine dyes of the formula I whereR⁴ is the radical -NHCOR⁸ or --NHCC₂ R⁸, where R⁸ is in either case asdefined above.

Particular preference is given to quinoline-methine dyes of the formulaI where

R¹ is chlorine,

R² is hydrogen or methyl,

R³ is hydrogen, and

K is a radical of the formula IIa or IIc where

R⁴ is hydrogen, methyl or acetylamino,

R⁵ is hydrogen or methoxy, and

R⁵ and R⁷ are each independently of the other hydrogen, benzyl orsubstituted or unsubstituted C₁ -C₈ -alkyl.

The quinolinemethine dyes of the formula I according to the presentinvention are preparable by methods known per se.

For example, a nitroso compound of the formula III

    K--N═O                                                 (III)

where K is as defined above, can be condensed with a quinoline of theformula IV ##STR4## where R¹, R² and R³ are each as defined above (seefor example DE-A-3 716 656).

It is also possible to couple amines of the formula V

    K--NH.sub.2                                                (V)

where K is as defined above, oxidatively with the quinolines of theformula IV (see for example U.S. Pat. No. 4,695,287).

It is a further object of the present invention to provide a novelprocess for the thermal transfer of dyes.

In the thermotransfer printing process, a transfer sheet which containsa thermally transferable dye in one or more binders on a substrate, withor without suitable assistants, is heated from the back with an energysource, for example a thermal printing head, in short pulses (lastingfractions of a second), causing the dye to migrate out of the transfersheet and diffuse into the surface coating of a receiving medium. Theessential advantage of this process is that the amount of dye to betransferred (and hence the color gradation) is readily controllablethrough adjustment of the energy to be emitted by the energy source.

In general, color recording is carried out using the three subtractiveprimaries yellow, magenta and cyan (with or without black).

To ensure optimal color recording, the dyes must have the followingproperties:

ready thermal transferability,

little tendency to migrate within or out of the surface coating of thereceiving medium at room temperature,

high thermal and photochemical stability and resistance to moisture andchemical substances,

suitable hues for subtractive color mixing,

a high molar absorption coefficient,

no tendency to crystallize out on storage of the transfer sheet.

These requirements are very difficult to meet at one and the same time.

For this reason most of the existing thermal transfer dyes do not havethe required combination of properties.

We have found that the object of a novel process for the thermaltransfer of dyes is achieved by a process for transferringquinolinemethine dyes from a transfer to a sheet of plastic-coated paperby diffusion or sublimation with the aid of an energy source, whichcomprises using a transfer with one or more quinolinemethine dyes of theformula I above.

Compared with the dyes used in existing processes, the dyes of theformula I to be transferred in the process of the present inventiongenerally possess improved migration properties in the receiving mediumat room temperature, readier thermal transferability, higher thermal andphotochemical stability, readier industrial accessibility, betterresistance to moisture and chemical substances, higher color strength,better solubility or better suitability for subtractive color mixing(higher purity of hue, more favorable shape of absorption bands). Theyare also particularly advantageously suitable for dye mixtures withtriazolopyridine dyes as described in earlier patent applicationEP-A-416 434. This is true chiefly in respect of better transferability,higher inked ribbon stability, higher light fastness, betterdistribution of the transfer dyes in the receiving medium and inparticular the preparation of better black mixtures.

To prepare the dye transfers required for the process of the presentinvention, the dyes are incorporated into a suitable organic solvent orinto mixtures of solvents together with one or more binders and possiblyassistants to form a printing ink in which the dye is preferably presentin a molecularly dispersed, ie. dissolved, form. The printing ink can beapplied to the inert substrate by knife coating and air dried.

Suitable organic solvents for the dyes I are for example those in whichthe solubility of the dyes I is greater than 1% by weight, preferablygreater than 5% by weight, at 20° C.

Examples which may be mentioned are ethanol, propanol, isobutanol,tetrahydrofuran, methylene chloride, methyl ethyl ketone,cyclopentanone, cyclohexanone, toluene, chlorobenzene and mixturesthereof.

Suitable binders are all resins or polymer materials which are solublein organic solvents and capable of binding the dye to the inertsubstrate in a form in which it will not rub off. Preference is givenhere to those binders which, after the printing ink has been air dried,hold the dye in a clear, transparent film in which no visiblecrystallization of the dye occurs.

Examples of such binders are cellulose derivatives, eg. methylcellulose,ethylcellulose, ethyl-hydroxyethylcellulose, hydroxypropylcellulose,cellulose acetate or cellulose acetobutyrate, starch, alginates, alkydresins, vinyl resins, polyvinyl alcohol, polyvinyl acetate, polyvinylbutyrate and polyvinylpyrrolidones. It is also possible to use polymersand copolymers of acrylates or their derivatives, such as polyacrylicacid, polymethyl methacrylate or styrene-acrylate copolymers, polyesterresins, polyamide resins, polyurethane resins or natural CH resins suchas gum arabic. Further suitable binders are described for example inDE-A-3 524 519.

Preferred binders are ethylcellulose, ethyl-hydroxyethylcellulose,polyvinyl butyrate and polyvinyl acetate.

The ratio of binder to dye may vary, preferably from 1 : 1 to 10 : 1.

Possible assistants are release agents as mentioned in EP-A-227 092,EP-A-192 435 and the patent applications cited therein, but also inparticular organic additives which prevent the transfer dyes fromcrystallizing out in the course of storage and heating of the inkedribbon, for example cholesterol or vanillin.

Inert substrate materials are for example tissue, blotting or parchmentpaper and plastics films possessing good heat resistance, for examplemetallized or unmetallized polyester, polyamide or polyimide. The inertsubstrate may additionally be coated on the side facing the thermalprinting head with a lubricant or slipping layer in order that adhesionof the energy source, in particular the thermal printing head, to thesubstrate material may be prevented. Suitable lubricants are describedfor example in EP-A-216 483 and EP-A-227 095. The thickness of thesubstrate is in general from 3 to 30 μm, preferably from 5 to 10 μm.

The dye-receiving layer can be basically any heat resistant plasticslayer which possesses affinity for the dyes to be transferred, forexample a modified polycarbonate or polyester. Suitable recipes for thereceiving layer composition are described in detail for example inEP-A-227 094, EP-A-133 012, EP-A-133 011, EP-A-111 004, JP-A-199997/1986, JP-A-283 595/1986, JP-A-237 694/1986 and JP-A-127 392/1986.

The transfer process is effected by means of an energy source, forexample a laser or a thermal printing head, which in the latter casemust be heatable to ≧300° C. in order that the transfer of the dye maytake place within the time range t: 0 <t <15 msec. In the course oftransfer, the dye migrates out of the transfer sheet and diffuses intothe surface coating of the receiving medium.

The dyes of the present invention are also advantageously suitable fordyeing synthetic materials, for example polyesters, polyamides orpolycarbonates, and in particular textile fabrics of polyester,polyamide or polyester-cotton blend fabrics.

The novel dyes are also advantageously suitable for the production ofcolor filters as described for example in EP-A-399 473.

They can also be used with advantage in the production of toners for usein electrophotography.

Further details concerning the preparation may be discerned from theExamples which follow, in which the percentages are by weight, unlessotherwise stated.

Preparation of dyes EXAMPLE 1

10 g of N,N-diethyl-p-phenylenediamine hydrochloride and 11.4 g of5,7-dichloro-8-hydroxy-2-methyl-quinoline were introduced into 300 ml ofethanol. Then a solution of 8.5 g of silver nitrate in 38 ml of waterwas added dropwise at room temperature with stirring. On completion ofthe addition 38 ml of 25% strength by weight of ammonium hydroxidesolution and then a solution of 21.3 g of silver nitrate in 25 ml ofwater were added to the reaction solution. After stirring at 30°-40° C.for 3 hours the reaction solution was filtered with suction, and thefilter residue was dried at room temperature under reduced pressure in adrying cupboard and then chromatographed over a column (silica gel/ethylacetate). The yield of spectrally ultrapure dye of the formula ##STR5##was 8 6 g. The dye had a melting point of 145° C. and an absorptionmaximum (measured in tetrahydrofuran) of 616 nm.

The same method was used to obtain the dyes described in more detail inthe following Table 1 and in the subsequent transfer experiments:

                                      TABLE 1                                     __________________________________________________________________________     ##STR6##                                                                     Example                         λ.sub.max                              No.  K R.sup.1                                                                         R.sup.6 R.sup.7                                                                             R.sup.5                                                                         R.sup.4                                                                              [nm].sup.a)                                                                       Rf value                                  __________________________________________________________________________    2    II.sub.c                                                                        Cl                                                                              CH.sub.3                                                                              --    --                                                                              CH.sub.3                                                                             648 0.45.sup.b)                               3    II.sub.c                                                                        Br                                                                              CH.sub.3                                                                              --    --                                                                              CH.sub.3                                                                             650 0.47.sup.b)                               4    II.sub.c                                                                        Cl                                                                              C.sub.2 H.sub.5                                                                       --    --                                                                              H      634 0.40.sup.b)                               5    II.sub.c                                                                        Br                                                                              C.sub.2 H.sub.5                                                                       --    --                                                                              H      637 0.33.sup.b)                               6    II.sub.c                                                                        Cl                                                                              C.sub.2 H.sub.4 CO.sub.2 C.sub.2 H.sub.5                                              --    --                                                                              H      620 0.30.sup.b)                               7    II.sub.c                                                                        Br                                                                              C.sub.2 H.sub.4 CO.sub.2 C.sub.2 H.sub.5                                              --    --                                                                              H      622 0.34.sup.b)                               8    II.sub.a                                                                        Cl                                                                              C.sub.2 H.sub.5                                                                       C.sub.2 H.sub.5                                                                     H NHCO.sub.2 CH.sub.3                                                                  643 0.38.sup.c)                               9    II.sub.a                                                                        Br                                                                              C.sub.2 H.sub.5                                                                       C.sub.2 H.sub.5                                                                     H NHCO.sub.2 CH.sub.3                                                                  647 0.35.sup.b)                               10   II.sub.a                                                                        Cl                                                                              C.sub.2 H.sub.5                                                                       CH(CH.sub.3).sub.2                                                                  H H      633 0.35.sup.b)                               11   II.sub.a                                                                        Br                                                                              C.sub.2 H.sub.5                                                                       CH(CH.sub.3).sub.2                                                                  H H      636 0.38.sup.b)                               12   II.sub.a                                                                        Cl                                                                              C.sub.2 H.sub.5                                                                       C.sub.2 H.sub.4 OCH.sub.3                                                           H CH.sub.3                                                                             628 0.27.sup.b)                               13   II.sub.a                                                                        Br                                                                              C.sub.2 H.sub.5                                                                       C.sub.2 H.sub.4 OCH.sub.3                                                           H CH.sub.3                                                                             631 0.27.sup.b)                               __________________________________________________________________________     .sup.a) measured in tetrahydrofuran                                           .sup.b) mobile phase 3:2 v/v toluene/ethyl acetate                            .sup.c) mobile phase ethyl acetate                                       

Transfer of dyes

For a simple quantitative examination of the transfer characteristics ofthe dyes, the thermal transfer was effected with large hotplates, thetransfer temperature being varied within the range 70° C. <T<120° C.while the transfer time was fixed at 2 minutes.

α) General recipe for coating the substrate with dye: 1 g of binder wasdissolved in 8 ml of 8:2 v/v toluene/ethanol at 40°-50° C. A solution of0.25 g of dye in 5 ml of tetrahydrofuran was added with stirring and, ifnecessary, insoluble residue was filtered off. The print paste thusobtained was applied with an 80 μm doctor blade to a polyester sheet(thickness: 6-10 μm) and dried with a hair dryer.

β) Testing of thermal transferability The dyes used were tested asfollows: The polyester sheet donor containing the in-test dye in thecoated front was placed face down on a sheet of commercially availablepaper receptor (further details below) and pressed down. Donor/receptorwere then wrapped in aluminum foil and heated between two hotplates atvarious temperatures T (within the temperature range 70° C. <T <120°C.). The amount of dye diffusing into the bright plastics layer of thereceptor is proportional to the optical density (=absorbance A). Thelatter was determined photo-metrically. The plots of the logarithm ofthe absorbance A of the colored receptor papers measured within thetemperature range from 80° to 110° C against the reciprocal of thecorresponding absolute temperature are straight lines from whose slopeit is possible to calculate the activation energy ΔE_(t) for thetransfer experiment: ##EQU1##

To complete the characterization, the plots additionally reveal thetemperature T*[° C.]at which the absorbance A of the colored receptorpapers attains the value 1.

The dyes listed below in Table 2 were processed according to α) and thedye-coated transfers obtained were tested for their transfercharacteristics according to β). The table shows in each case thethermotransfer parameters T* and ΔE_(T), the absorption maxima λ_(max)(measured in tetrahydrofuran) and the binders used.

The key to the abbreviations is as follows:

B binder

EC ethylcellulose

MX mixture of polyvinyl butyrate and ethylcellulose in a weight ratio of2:1

V =Vylon®290 (from Toyobo)

    __________________________________________________________________________     ##STR7##                                                                     Exam-                                                                         ple                                              λ.sub.max                                                                      ΔE.sub.T       No. K R.sup.1                                                                         R.sup.2                                                                             R.sup.6                                                                              R.sup.7  R.sup.5                                                                           R.sup.4   R.sup.3                                                                         B  [nm]                                                                              T*[°C.]                                                                    [kcal/mol]           __________________________________________________________________________      14*.sup.)                                                                       IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   H         H V  616 92  16                   15  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   NHCOCH.sub.3                                                                            H MX 649 95  13                   16  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   NHCO.sub.2 C.sub.2 H.sub.4 OC.sub.2                                           H.sub.5   H EC 651 98  12                   17  IIc                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      --       --  CH.sub.3  H V  651 101 16                   18  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.4 H.sub.9                                                                      C.sub.2 H.sub.5                                                                        H   H         H V  617 94  14                   19  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.4 H.sub.9                                                                      C.sub.2 H.sub.5                                                                        H   CH.sub.3  H V  635 95  15                   20  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.4 H.sub.9                                                                      CH.sub.2 CH(CH.sub.3).sub.2                                                            --  CH.sub.3  H EC 618 96  17                   21  IIc                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      --       --  H         H EC 635 100 13                   22  IIa                                                                             Br                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   H         H EC 617 100 17                   23  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.4 H.sub.9                                                                      C.sub.4 H.sub.9                                                                        H   H         H EC 619 103 12                   24  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   CH.sub.3  H EC 633 89  14                   25  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.4 H.sub.9                                                                      C.sub.4 H.sub.9                                                                        H   CH.sub.3  H EC 636 118 13                   26  IIc                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.4 OC.sub.4 H.sub.9                                                     --       --  CH.sub.3  H V  646 110 12                   27  IIa                                                                             Cl                                                                              CH.sub.3                                                                            H      CH(CH.sub.3).sub.2                                                                     OCH.sub.3                                                                         H         H EC 623 99  15                   28  IIa                                                                             Cl                                                                              CH.sub.3                                                                            C.sub.2 H.sub.5                                                                      C.sub.2 H.sub.5                                                                        H   H         Cl                                                                              EC 647 97  15                   29  IIa                                                                             Cl                                                                              CH(CH.sub.3).sub.2                                                                  C.sub.4 H.sub.9                                                                      C.sub.4 H.sub.9                                                                        H   CH.sub.3  H V  636 98  16                   __________________________________________________________________________     *.sup.) The dye of example 14 is the product described in Example 1      

We claim:
 1. A quinolinemethine dye of the formula I ##STR8## where R¹is fluorine, chlorine or bromine,R² is hydrogen or C₁ -C₄ -alkyl, R³ ishydrogen, fluorine, chlorine or bromine, and K is a radical of theformula ##STR9## where R⁴ is hydrogen, methyl, methoxy, C₁ -C₄-alkylsulfonylamino, C₁ -C₄ -monoalkylaminosulfonylamino, C₁ -C₄-dialkylaminosulfonylamino, -NHCOR⁸ or -NHCO₂ R⁸, where R⁸ is phenyl,benzyl, tolyl or C₁ -C₈ -alkyl which may be interrupted by one or twooxygen atoms in ether function,R⁶ is hydrogen, C₁ -C₈ -alkyl which maybe substituted and which may be interrupted by one or two oxygen atomsin ether function, or C₅ -C₇ -cycloalkyl.
 2. A quinolinemethine dye asclaimed in claim 1, whereinR¹ is chlorime, R² is hydrogen or methyl, andR³ is hydrogen.